Propane is no better than oil in terms of cost per BTU (except propane boilers are usually slightly more efficient). Natural Gas (from the street) is significantly cheaper than either oil or propane and particularly if used with a modern condensing boiler.

It’s not that a heat pump isn’t more efficient it’s that if you have forced hot water or steam radiators you are looking at an additional $40K to retrofit forced air ducting to your house. Oh and you still need a solution for domestic hot water, probably you’ll just end up with a resistive heater (or a hybrid/heat pump unit like the Aerotherm but the heat has to come from the room).

I went off median prices from DOE and found oil to come in at 32 cents per 10,000 BTU's propane at 24 cents per 10,000 BTU.

You can look at the State of New Hampshire’s Dept of Energy comparisons here, updated weekly:

https://www.energy.nh.gov/energy-information/nh-fuel-prices

Actually right now #2 heating oil is now somewhat cheaper per MBTU than propane. Also Natural Gas is slightly cheaper than heat pump per MBTU (YMMV on efficiency!)

I’ve never seen propane cheaper than heating oil here!

EDIT: It’s probably worth pointing out that the North East of the US is the largest heating oil market in the world.

ooh, thats a great source - now that I've updated my calculator, your numbers match mine - I went with local prices for propane and DOE prices for propane.

Exceed 15 c/kWh? We were past that loooooong ago in California. Here are PG&E's rates for the Bay Area... https://www.pge.com/assets/pge/docs/account/rate-plans/resid...

The cheapest rate is 38c/kWh, the most expensive is 62c/kWh..